Reactive oxygen species work as a cause material of skin aging. When skin is exposed to UV light, photochemical reactions continually occur at the skin so as to produce reactive oxygen species. These reactive oxygen species may damage skin cells or tissue. They destroy an antioxidant defence layer, consisting of antioxidant enzymes and non-enzymatic antioxidants, thereby shifting the balance of oxidants/antioxidants to the oxidative state. Such oxidative stress may lead to damage of living body components, such as lipid peroxidation, protein oxidation, activation of protease that destroys skin components, chain scission of collagen and elastin, which are elastic fibers, and abnormal cross conjugation thereof, chain scission of hyaluronic acid, promotion of melanin synthesis, and DNA oxidation. In addition, such damage of living body components may lead to various aging effects such as skin wrinkle formation, elasticity reduction and widening of skin pores. Although there have been many studies on skin aging such as skin wrinkle formation and skin elasticity reduction, few studies have been made of skin pores. However, the most important factor of skin pore widening is also oxidative stress.
The structural change of skin according to oxidative stress is that the thicknessess of the epidermis, dermis and subcutaneous are reduced. In addition, the ECM (extracellular matrix) of the dermis, which relates to elasticity and tensility of skin, is changed. The ECM consists of two components. One is elastic fiber, which comprises about 2-4% of the ECM, and the other is collagen, which comprises about 70-80% of the ECM. Under the influence of oxidative stress, collagen is decomposed so that collagen in the skin is reduced. As a person grows older, the ECM around skin pores is reduced; thereby skin pores widen.
Thus, the best solution to prevent the widening of skin pores is to inhibit oxidative stress, and the best solution to reduce the size of the widened skin pores is to increase the production of collagen around skin pores.
Although not directly related to the widening of skin pores, there have been many studies on antioxidants to inhibit oxidative stress, and many antioxidants have been actually developed, however, not all of them are effective for increasing collagen biosynthesis or reducing skin pore size.
Meanwhile, vitamin C and vitamin E are two antioxidants generally used. Vitamin C is a water soluble antioxidant, and vitamin E is a fat soluble antioxidant. Although these antioxdiants show strong antioxidant effects, they can easily deteriorate when exposed to air, due to their instability. Thus, there is much limitation on their use. Another possible antioxidant is polyphenol. However, it also shows instability.